1. Field of Invention
The present invention relates to a composition (a discharge composition) that can be used for the formation of thin films of functional materials, especially for the formation of patterned films of functional materials using discharge devices, and that can stably be discharged. The invention also relates to a method for producing a uniform film (a functional film) using the composition, to a functional element, to a method for producing the functional element, to a method for producing an electro-optical device and to a method for producing electronic apparatus.
2. Description of Related Art
Thin films can be produced from liquid phases by a wide variety of processes, such as by a spin coating process, a sol-gel process and a blade process. According to these processes, a composition containing a material, as a solute that is dissolved or dispersed in a solvent, is applied to a substrate, and the solvent is removed, for example, by heating, to thereby yield a functional thin film.
Such functional materials have conventionally been patterned by a photolithography process in many cases. However, the photolithography process is subject to disadvantages, such as high cost, complicated steps and large amounts of materials consumed. Accordingly, fine patterning techniques of functional materials using discharge devices, especially using ink-jet printing devices, have been examined, since such discharge devices entail low costs and simple steps. Examples of products of fine patterning of functional materials using ink-jet printing devices include: color filters (Japanese Unexamined Patent Application Publications No. 9-329706 and No. 11-202114) and organic EL display devices (Japanese Unexamined Patent Application Publications No. 7-235378, No. 10-12377 and No. 10-153967). As such discharge compositions, a composition for organic EL elements for easily patterning a thin film in a short time with high precision and for easily optimizing a film design and light-emitting characteristics is disclosed in Japanese Unexamined Patent Application Publication No. 11-40358, and a discharge composition for easy and precise pattering in a short time without curving of the discharged composition or clogging is disclosed in Japanese Unexamined Patent Application Publication No. 11-54270.
The present invention provides a composition including a solvent and a functional material. The solvent includes at least one heterocyclic compound having one or more substituents and containing an oxygen atom as a constituent atom. The functional material is selected from the group including organic EL materials, conductive materials, insulative materials and semiconductive materials.
The present invention also provides a method for producing a film. This method includes the step of applying the composition as a pattern to thereby form a thin film.
The present invention also provides a method for producing a functional element. This method includes the step of forming the functional thin film.
The present invention further provides a functional element that is made from the composition.
The present invention provides a method for producing an electro-optical device. This method includes the step of forming a functional thin film according to the aforementioned method.
In addition, the present invention provides a method for producing electronic apparatus. This method includes the step of forming a functional thin film according to the aforementioned method.
The patterning process using discharge devices, especially using ink-jet printing devices, does not require any plate making, can save resources, can save labor and has very satisfactory characteristics, but is subject to the disadvantage that materials for use in discharge compositions are limited, as mentioned below.
First, some of nonpolar or less polar functional materials or polymeric materials are insoluble or slightly soluble in solvents, such as water or alcohols, used in the ink-jet process, and solvents, such as water or alcohols, cannot be used in functional materials that are reactive with, or decomposed by, these solvents.
Second, when a material having low solubility in the solvent is used, a solution having an optimal concentration for film formation induces an ingredient to be precipitated after the preparation of the composition or causes clogging upon discharge. In contrast, when a solution having a low concentration is used to avoid clogging upon discharge, the number of discharge procedures of the composition must be increased to thereby increase the number of steps in order to prepare a functional film having a sufficient film thickness so as to exhibit the characteristics of the functional material.
Third, when an organic solvent having a high vapor pressure is used as the solvent in the functional material, evaporation of the solvent deprives the discharge composition of vaporization heat to thereby accelerate deposition of the functional material upon discharge or during film formation after discharge. Thus, the solvent is evaporable, and thereby induces deposition and clogging of the functional material. When the functional material is a multicomponent system, the resulting film induces phase separation, becomes heterogeneous and thereby loses its functions as the functional film.
Fourth, the resulting thin film formed by the ink-jet process may exhibit an irregular film thickness, such as a thin center and thick periphery, during drying procedure after application of the composition, and the film thickness cannot significantly be controlled.
Accordingly, the present invention provides a composition that can use nonpolar or less polar functional materials, functional materials reactive with solvents, such as water or alcohols, or polymeric materials in the formation of thin films of such functional materials, especially in the formation of patterned films of the functional materials using discharge devices. The present invention also provides a composition that can stably be discharged without clogging upon discharge or curving of the discharged composition in the application of the composition by the ink-jet process. The present invention also provides a method for producing a film, which method can produce a uniform and homogenous thin film using the composition, a functional element, especially an organic EL element, and a method for producing the same, as well as to provide methods for producing an electro-optical device and electronic apparatus that each have the functional element, and specifically to provide an organic EL display device having the functional element.
The composition (especially a liquid composition) in accordance with an embodiment of the present invention includes a solvent and a functional material. The solvent includes at least one heterocyclic compound having one or more substituents and containing an oxygen atom as a constituent atom, and the functional material is selected from the group including organic EL materials, conductive materials, insulative materials and semiconductive materials.
The composition has the following advantages. Specifically, functional materials for use in the composition are not specifically limited, and nonpolar or less polar materials or reactive materials that are susceptible to reactions with water can be used without deteriorating their functions. In addition, the resulting composition can prevent or reduce, due to high solubility of constitutive materials, deposition of ingredients after the preparation of the composition or clogging upon discharge in the ink-jet process.
The heterocyclic compound in the composition preferably has a furan skeleton. By this configuration, the resulting composition can prevent or reduce, due to high solubility of constitutive materials, deposition of ingredients after the preparation of the composition or clogging upon discharge and can stably be discharged in the ink-jet process.
The heterocyclic compound in the composition preferably has a boiling point of equal to or more than 170xc2x0 C. By this configuration, the resulting composition can prevent or reduce deposition of the solute after the preparation of the composition or clogging upon discharge due to evaporation of the solvent and can stably be discharged.
The heterocyclic compound in the composition is preferably 2,3-dihydrobenzofuran. This configuration has an advantage in that functional materials for use in the composition are not specifically limited, and that nonpolar or less polar materials or reactive materials that are susceptible to reactions with water can be used without deteriorating their functions. In addition, the resulting composition can prevent or reduce, due to high solubility of constitutive materials, deposition of ingredients after the preparation of the composition or clogging upon discharge and can stably be discharged in the ink-jet process.
In the composition, the solvent that includes at least the oxygen heterocyclic compound preferably further includes another organic solvent. By this configuration, the resulting composition can prevent or reduce deposition of ingredients after the preparation of the composition or clogging upon discharge due to evaporation of the solvent and can stably be discharged. This composition also has an advantage in that the composition can have a controlled viscosity appropriate for the application, and the target functional film can easily be designed.
The composition that includes the other solvent preferably includes a benzene derivative as the other solvent. By this configuration, the resulting composition can prevent or reduce deposition of ingredients after the preparation of the composition or clogging upon discharge due to evaporation of the solvent and can stably be discharged. This composition also has an advantage in that the composition can have a controlled viscosity appropriate for the application, and the target functional film can easily be designed.
The method for producing a film in accordance with another embodiment of the present invention includes the step of applying the composition as a pattern to thereby form a thin film. This production method can prevent or reduce irregular film thicknesses during drying procedure after the application of the composition and phase separation of ingredients, and can yield uniform and homogeneous functional films.
In the method for producing a film, the composition is preferably applied with a discharge device. This configuration can easily yield finely patterned functional films at low costs.
The discharge device in the production method just mentioned above is preferably an ink-jet device. This configuration can easily yield finely patterned functional films at low costs without plate making.
In the method for producing a film, it is preferred that the composition is applied onto a substrate, and the substrate carrying the composition is subjected to heat treatment and/or pressurization or pressure reduction. This configuration can prevent or reduce irregular film thickness and phase separation of ingredients, and can yield uniform and homogeneous functional films.
The method for producing a functional element in accordance with yet another embodiment of the present invention includes the step of forming the functional thin film.
In the method for producing a functional element, a film that includes an organic EL material is preferably formed as the functional thin film.
The functional element in accordance with another embodiment of the present invention is made from the composition.
The functional element is preferably an organic EL element.
The method for producing an electro-optical device in accordance with yet another embodiment of the present invention includes the step of forming the functional thin film. Such an electro-optical device is specifically preferably an organic EL display device.
In addition, the method for producing electronic apparatus in accordance with a further embodiment according to the present invention includes the step of forming the functional thin film.
The composition provided by the present invention is a composition for use in the formation of patterned films of functional materials and includes a solvent and a functional material. The solvent includes at least one heterocyclic compound having one or more substituents and containing an oxygen atom as a constituent atom, and the functional material is selected from the group including conductive materials, insulative materials and semiconductive materials.
Functional materials for use in the composition are not specifically limited, and nonpolar or less polar materials or reactive materials that are susceptible to reactions with water can be used. Such functional materials include materials corresponding to the use of the composition of the present invention, such as organic EL (electroluminescence) materials and other light-emitting materials, organometallic compounds and other conductive materials, dielectric or semiconductive materials. Among these materials, organic EL materials are preferred.
The composition provided by the present invention is used for the formation of thin films of functional materials, especially for the formation of patterned films of such functional materials using discharge devices.
Solvents that each include at least one heterocyclic compound having one or more substituents and including an oxygen atom as a constituent atom are preferably used as the solvent for use in such a composition that includes the material as a solute and is stable after preparation of the composition and during application procedure of the composition. More preferably, the heterocyclic compound has a furan skeleton.
Such heterocyclic compounds may be either monocyclic heterocyclic compounds or condensed heterocyclic compounds. They may be heterocyclic compounds that each include a hetero atom, such as oxygen atom, nitrogen atom or a sulfur atom, and having two or more carbon atoms.
The substituents are not specifically limited and include, for example, straight- or branched-chain aliphatic hydrocarbon groups, alicyclic hydrocarbon groups and aromatic hydrocarbon groups.
Examples of such heterocyclic compounds are tetrahydrofuran, furan, oxazole, isoxazole, furazane, benzofuran, 2,3-dihydrobenzofuran, 1,2-benzisoxazole and 2-methylbenzoxazole.
The solvent may be a single solvent including one of the heterocyclic compounds, or a mixed solvent including two types or more of the heterocyclic compounds. Alternatively, the solvent may be a mixture including the heterocyclic compound and another solvent other than the heterocyclic compound. Benzene derivatives are preferred as the solvent other than the heterocyclic compound. Examples of such benzene derivatives are cymene, tetralin, cumene, decalin, durene, cyclohexylbenzene, dihexylbenzenes, tetramethylbenzenes and dibutylbenzenes. By using these solvents, the composition can have a controlled viscosity that is appropriate for the application, and the target functional film can easily be designed.
The aforementioned composition includes highly soluble materials, and can therefore prevent or reduce deposition of ingredients after the preparation of the composition. A solvent for use in the formation of a patterned film of a functional material using the ink-jet process preferably has high solvency for the functional material, and has a high boiling point and/or a low vapor pressure to prevent clogging upon discharge or curving of the discharged composition due to evaporation of the solvent or deposition of ingredients and to stably be discharged. Such a solvent more preferably has a boiling point of equal to or more than 170xc2x0 C., and a vapor pressure at room temperature of from 0.10 to 10 mm-Hg.
Any process such as a spin coating process, a dipping process, a casting process and a blade process can be applied to the method for producing a thin film using the composition.
Processes using discharge devices are typically preferred as a process for fine patterning of a functional material for their low costs and simple steps. Among these processes, the ink-jet printing process is specifically preferred.
The target functional film is prepared according to a technique, such as air-drying, heating, pressurization or pressure reduction, gas-flow drying, or combinations of these techniques, during or after the application of the composition onto the substrate.
The above production method can yield a uniform and homogenous functional film without irregular film thickness or phase separation of ingredients. By using procedures to remove the solvent in combination, the target functional film can easily be designed.
The functional element can yield a colored organic EL element when the ink-jet process is employed.